PEEK (polyether ether ketone), an aromatic linear high molecular polymer, not only has good processing performance, but also has excellent high-temperature resisting property. The load thermal deformation temperature of PEEK is as high as 315° C. and the temperature of continuous use is up to 260° C. Meanwhile, such polymer also has many remarkable performances of resisting abrasion, chemicals, fire, hydrolysis, radiation and the like. Therefore, in addition to the application in national defense and military, PEEK can also be widely used in such fields as aviation, automobile manufacturing, electronic apparatus, medical treatment, food, etc.
Structurally, PEEK is a polymer formed by the connection of ether bonds, ketone groups and aromatic rings. The chemical formula of PEEK is shown below:

wherein the R group connected between the two ether bonds can be benzene, biphenyl or terphenyl, and therefore the preparation for PEEK can be carried out with hydroquinone, diphenol and diphenol triphenyl as initiators.
The synthesis method of PEEK was successfully developed for the first time by UK Victrex PLC in the late 1970s and put into industrial production in 1987, in which the preparation for PEEK was carried out through solution polycondensation reaction with diphenyl sulfone as the solvent in a salt-mixed system of K2CO3/Na2CO3 and with 4,4′-difluorobenzophenone (or 4,4′-dichlorobenzophenone) and hydroquinone as raw materials; afterwards, countries throughout the world went deep into the research, wherein the European Patent EP 0174207 reported the preparation process of PEEK through Friedel-Crarts reaction with AlCl3 as a catalyst, the U.S. Pat. Nos. 6,881,816 and 6,566,484 applied by India Charda Corporation disclosed the preparation process of PEEK under a low temperature of 40 to 160° C. with phenoxyl-phenoxy benzoic acid as the only monomer and alkyl sulfonic acid as the solvent, and the Chinese Patent CN1050615C showed the preparation for a random copolymer of PEEK through high-temperature polycondensation of three monomers (4,4′-difluorobenzophenone, hydroquinone and diphenol) with the salt-mixed system of three components (Na2CO3/K2CO3/SrCO3) as a condensing agent. So far, however, the existing technology for preparing PEEK with Na2CO3 as the only condensing agent has not been found yet.
In the existing technology for preparing PEEK, great advantages, either in terms of the product quality or the technological maturity, can still be found in the process of preparing PEEK through polycondensation of dihydroxy phenol and difluorobenzophenone. According to the experimental results disclosed, however, the salt-mixed system of K2CO3/Na2CO3 or K2CO3/Na2CO3/SrCO3 is mostly adopted as the condensing agent and particularly the composite condensing agent with K2CO3 as the main component; but the composite condensing agent has the following problems: the content of impurities in the product is high due to strong water absorption of potassium carbonate and difficult crushing as well as screening; one-step charging cannot well control the viscosity of the PEEK product, which affects the batch stability of the product and meanwhile has certain impact on industrial production. In the condensation reaction, diphenol needs to first form corresponding phenol sodium or potassium salts together with sodium carbonate or potassium carbonate, wherein the activity of the phenol potassium salt is higher than that of the phenol sodium salt; therefore, the PEEK product with higher molecular weight can be easily generated during the polycondensation with difluorobenzophenone, but at the later stage of the reaction the probability of molecular collision lowers, the molecular weight can hardly increase to be high enough and the distribution of molecular weight is quite wide due to higher system viscosity; when sodium carbonate is used as the only condensing agent, the reaction is difficult to continue as soon as the molecular weight increases to a certain extent due to lower activity of the sodium carbonate; therefore, the PEEK product with lower molecular weight rather than that with higher molecular weight can usually be prepared.